Cooling pellets



April 6, 1965 A. w. STORM ETAL COOLING PELLETS 7 Shets-Sheet 1 Filed May 15, 1963 7 Sheets-Sheet 2 April 6, 1965 A. w. STORM ETAL COOLING PELLETS Filed May 13, 1965 April 6, 1965 A. w. STORM ETAL COOLING PELLETS '7 Sheets-Sheet 3 Filed May 13, 1963 Apfil 6, 1965 A. w. STORM ETAL COOLING PELLETS '7 Sheets-Sheet 4 Filed May 13., 1963 7// 4 m r q\\\\ .u

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COOLING PELLETS Filed May 15, 1967 '7 Sheets-Sheet 5 7 Sheets-Sheet 6 A. W. STORM ETAL COOLING PELLETS April 6, 1965 Filed May 13, 1965 April 6, 1965 A. w. STORM ETAL COOLING PELLETS '7 Sheets-Sheet '7 Filed May 15, 1963 United States Patent 3,176,969 t'JOOLlWG PELLE'KS Arthur W. Storm and Frank G. Rinlrer, Toledo, @hio, assignors to Midland-Ross Corporation, Toledo, Ghio, a corporation of Ohio Filed May 13, 163, Ser. No. 279,997 16 Claims. (U. 26329) This invention relates to the art of indurating small balls (pellets) of finely divided solid materials by forcing high temperature heating gas (e.g., heated air) countercurrently through the upper part of a column of such balls gravitationally descending through a treating furnace, and is concerned with an improvement in the subsequent step of cooling the so-heated balls. The improvement presents both process and apparatus aspects.

In this general process, as illustratively described in, for instance, U.S. Patents Nos. 2,676,095 and 3,003,756, the initially substantially unheated and moist (i.e., green) balls are transported, from a device in which the balls are formed, to the mouth of the furnace and are deposited therein, on the stockline of a column of like balls. As the column gravitationally descends through the furnace the initially green balls are dried and quickly heated, in the upper part of the column, to a suitable predetermined indurating temperature (e.g., a temperature of the order of 2,300 F.), by means of a current of highly heated heating gas (e.g., air or gas mixture having a net oxidizing elfect) which latter is caused to move countercurrently through the upper part, only, of said column. customarily, in this stage of the process, a current of cooling air is countercurrently forced through or substantially all of the column, the same minglingat near the top of the column-with the hightemperature heating gas introduced at that level. Thereafter, during the subsequent dwell of the resulting indurated pellets in the furnace, sometimes called the cooling stage of the process, the temperature of the pellets gradually drops from its maximum to some level intermediate the latter and ambient temperature. What this intermediate level may be depends on a number of variables, including: maximum attained temperature of the pellets; speed of descent of the column; relative amount of cooling air employed; desired discharge temperature; etc.

That some mode of cooling the freshly indurated pellets is technologically necessary follows from the fact that in the absence of a positive cooling step the pellets may discharge at an elevated temperature, in excess of 600 F., thus creating a special problem in the handling of the highly heated product.

With reference to the above-mentioned recourse to cooling by means of a countercurrent stream of cooling air, it should be noted that the extent of the cooling thus realizable was very circumscribed, in view of the limitations, on the relative amount of air used, imposed by the necessary over-all heat balance.

It heretofore had been attempted to effect significant cooling of the pellets by discharging them from the indurating furnace per se into a separate chamber where the pellets were subjected (a) to cooling by means of atomized water (mist cooling), or (b) as suggested in the above-mentioned Stefiensen Patent No. 3,003,756, to cooling by a countercurrent stream of cooling gas. To carry into effect either of these expedients, it is necessary to elevate the furnace structure a considerable distance into the air, thereby materially adding to the expense both of the apparatus itself and 0f the enclosure within which the apparatus is housed.

It heretofore had been suggested to cool a column of gravitationally descending fluent solids by forcing cool- "ice ing air transversely through the column, from one side thereof to the other. This is possible to a limited extent only, and is technologically unfeasible because of the high pressure necessary for forcing the air across the column.

Prior experiments had indicated that it was not only feasible but very advantageous to carry out a positive cooling step in the furnace shaft itself, as opposed to cooling in a separate chamber or vessel disposed beneath the furnace, by introducing a current of cooling gas (e.g., atmospheric air) at superatmospheric pressure into the interior of the column of pellets resident in a lower portion of the furnace shaft, e.g., in the bifurcated parts, or legs, of the shaft furnace shown in the Steffensen patent, and providing means, in opposite walls of the shaft and generally opposite to the locus of cooling gas introduction, for the cooling gas to disengage itself from the pellets and to exit from the shaft. This gas-disengaging means preferably takes the form of a fixed or stationary screen composed of an array of parallel slats or bars generally vertically disposed in the wall of the furnace shaft, the bars being spaced apart a distance (cg, approximately three-eighths of an inch) calculated to be too small to permit the passage of pellets therebetween. These bars may, and preferably do, have a length equal to the vertical dimension of a rectangular aperture (or window) let into the wall of the furnace shaft at a level well below the chunk breakers and in the lower part of the shaft, and width of approximately three inches and a thickness or" approximately threefourths of an inch, this latter dimension diminishing in the direction away from the pellets column, by virtue of a taper imposed upon the bars, so as to avoid jamming of solids in the space between two adjacent bars.

This general concept is advantageous in a number of respects. Thus, it permits a very substantial shortening of the furnace structure (and consequently lowering of the building housing the furnace). As regards the cooling function, however, the results are believed to be unacceptable from a practical viewpoint, because of the following circumstance. It has been found, experimental- 1y, that at the outset, relatively free outward flow of the cooling gas, through this stationary screen, occurs and the same continues at practically a steady rate for some (e.g., two, three or four) hours until bridging of the interstices of the screen starts; then, back pressure builds up, and flow falls off very rapidly as a chain reaction of bridging ensues. Thereafter, only a slight flow of gasat practically a steady rate-occurs. Thus in one observed test the initial flow of gas through the stationary screen was substantially steady for four hours, at the end of which period bridging was noticeably beginning. In the ensuing hour (or thereabouts) the rate of flow drastically fell oil to a trickle, and thereafter continued at this insignificant rate. By bridging is here meant the adventitious cooperation of two or more particles (broken off from pellets) in building a bridge across the slot-like opening between two adjacent bars of the screen thereby promoting the build-up of a dam or pellet fragments and dust particles (of varying sizes).

We have discovered that this rapid drop-oif in gas flow, through a screen of bars integrated into the furnace wall, can be entirely avoided, and normal flow with relatively small back-pressure and at a substantially steady rate can be maintained indefinitely, by intermittently or continuously oscillating or vibrating all or at least some of the bars composing the screen, the oscillation or vibration having an amplitude merely surlicient to dislodge bridging particles and to allow the components of such bridges to pass through the interstices.

We have found that by this improved procedure we were able, in one specific test characteristic of the presently improved process by passing about 0.7 pound of atmospheric air per each 1.0 pound of highly heated pellets of iron ore concentrates through the column of pellets, to reduce the average exit temperature of the pellets from say 665 F. to a 300- F. average. In this connection it is to be noted that average temperatures, only, can be mentioned, it'being the fact that both in the absence of cooling and with the aid of cooling, the pellets exit from the furnace shaft at varying (non-uniform) temperatures depending on the history of the peak temperatures attained during the firing period and the relative volume of cooling gas coming into contact with any one pellet.

In a specific proposed case, approximately 1680 pounds per minute of indurated pellets, at an average temperature of 700 F., were descending through each of the two legs or hoppersof generally rectangular cross-section-of the furnace shaft. On opposite sides of one of the hoppers there were'provided, in suitable furnace wall apertures therefor, a total of four panels of disengaging screen, each screen panel having inside dimensions of 38 inches by 30 inches and presenting approximately 31% of free openings, i.e., the interstices between the generally parallel bars or slats, of tapered cross-section, presenting at their ends adjacent the pellets column a slot threeeighths of an inch in width. Each screen panel presented 960 lineal inches of three-eighths inch slot. Oscillation means (equivalent to oscillating means about to be described) were associated with the screen bars, and these means oscillated every other bar by a stroke of about 0.5 inch at a rate of 20 oscillations per minute for an interval of 0.5 minute per period of 4 hours of operation. The static pressure within the column of pellets resident in .the leg of the furnace was about 7 pounds per square inch, and there was a pressure of about 2 pounds per square inch on the outside of the screen. The pressure of the introduced cooling air was 7.5-8.0 pounds per square inch.

Under these conditions, there were disengaged from the column 4 s.c.f.m. (standard cubic feet per minute) of spent cooling gas per lineal inch of slot or 15,360 s.c.f.m. of the gas through the total of four screen panels. The cooling gas (air) had been introduced into the center of the pellets column resident in the furnace leg, at the level of said apertures, at ambient temperature (about 60 F.) at disengagement, its average temperature was about 510 F. By virtue of this amount of cross-cooling, the pellets discharged from the furnace at an average temperature of 325 F., whereas prior to this test they had been discharging from the furnace at an average temperature of 670 F. The stated amount of oscillation was found to have prevented or greatly minimized the build-up of bridging aggregates of particles at the aforesaid slots: the back-pressure was maintained substantially constant throughout the test. As an illustration of the general capability of the above-described cooling procedure, it has been calculated that 0.5 lb. air/lb. pellets can reduce mean pellet temperature-from 665 F. to 300 F. with a range of pellet temperatures of from 100 F. to 625 F., whilst the use of 0.7 lb. air/lb. pellets can reduce the range of pellet temperatures from 100 F. to 450 F.

'while holding the 300 F. mean.

The apparatus of the present invention is a treating furnace,-e.g., indurating furnace, of the vertical shaft type the lowermost part of which has been modified by the integration thereinto of the novel crosscooling apparatus of the present invention. In its broadest concept the modification consists essentially in providing (a) a cooling gasintroducing means within the shaft, or one or both legs or hoppers of the shaft (in case the furnace is bifurcated at its lower part), and at a locus preferably substantially equidistant from opposite side walls of the shaft or hopper, and (b) in each of said opposite walls, and preferably at a level generally opposite said cooling gas-introducing means, a gas-disengaging screen means of improved de- 4 sign, said creen communicating between the interior of the shaft (or, hopper) and a housing secured to the wall of the shaft or hopper. Said screen means includes not only a screen per se but also (c) a component functioning to oscillate or vibrate parts of the screen. As anyone skilled in the indurating. art will appreciate, the apparatus also must include suitable (d) conduit means for conducting cooling gas, under the desired superatmospheric pres sure, from any conventional source thereof through the wall of the shaft (or hopper) and to the aforesaid cooling gas introducing means. Also, it is preferable that the dust-laden, spent cooling gas, after having been disengaged from the'pellets column into said housing, be diverted some distance from the furnace to a place where the heat and dust may be tolerated, for which purpose the apparatus preferably includes also suitable (e) diverting conduit means communication between said housing and such place, which diverting conduit means may and preferably does comprisea device for abstracting coarser or heavier solid particles from the effluent gas.

In general, the screen is composed of substantially parallel bars spaced apart to provide between adjacent bars slot-like open spaces functioning to screen out the pellets and to disengage the spent cooling gas, some of the bars being movable to a limited extent with respect to adjacent bars. The screen is provided with motion- I effecting means operatively associated with said movable bars for effecting relative motion between said movable bars and said adjacent bars to disengage any solid material tending to obstruct said open spaces.

In the preferred construction, the screen itself is composed of a plurality of substantially parallel generally vertically disposed bars which are spaced apart from each other to provide therebetween gas removal slots having a width calculated to limit the size of a solid particle, carried therethrough, to an acceptable maximum. The critical spacing is that which will not pass a pellet of the least suitable diameter. Thus, in one instance of indurating pellets of iron ore concentrates the critical spacing was three-eighths inch and the minimum pellet diameter wasvery slightly in excess of this value. Each bar is tapered so that the space between adjacent bars increases in width as it recedes from the shaft or hopper whereby to minimize the tendency for particles to wedge after they enter said space. Every other bar is pivoted at. one end, and is functionally associatedintermediate its ends-with means for oscillating or vibrating the bar: the intervening bars may be and preferably are stationary. Said oscillating means may be of the cam type but preferably comprises pressure fluidactuated reciprocating motor (e.g., a compressed air cylinder and piston) and pivotal linkage between the motor (e.g., piston) and the bar for imparting limited oscillatory movement of the bar about its pivot. Said linkage includes individual rearwardly outstanding knuckles or lugs secured to the pivoted bars at about their midpoints, a rod extending through each of the knuckles, and an articulater connecting bar between said rod and the reciprocating part of said motor. The reciprocating motor is furnished with suitable manual and automatic controls for actuating said motor, and hence for oscillating said pivoted bars, either continuously or intermittently for any predetermined interval of oscillation. The periodic relative motion of alternate bars dislodges jammed particles (bridges) and frees the gas-disengaging slots of the screen.

While continuous oscillation of the movable bars makes for an operable process, we foresee no situation in which the same would be necessary. To the contrary, We have found itfeasible to oscillate the movable bars only as and when the same is necessary for dislodging jammed particles and for maintaining the back pressure substantially constant. 'Thus, we prefer to oscillate them for a fraction of a minute each 30 minutes, or at least two complete cycles each 4 hours. Preferably, we as cillate at a rate of 8-10 seconds per cycle (in and out movements), with a stroke of from about one-half inch to as much as one inch at the free ends of the bars (at the cylinder, about three-eighths inch).

Preferably, the bars are about 3 inches thick (front to back).

In the event the screen means resident at any one shaft (or, hopper) wall consists of a pair (or more) of similar panels of screen, the pivoted bars of each screen panel may be oscillated independently of the bars of the other panel or panels, or they may be associated in gang fashion and oscillated from a single oscillating means.

As was mentioned hereinbefore, the means for providing periodic motion to the pivoted bars may consist essentially of a cam drum, held against the bars by suitable C clamps or brackets, in association with conventional means for rotating (or, oscillating) the cam drum.

To allow for expansion, the stationary bars are so dimentioned, with respect to the frame of the screen panel, as to provide a substantial gap between the lower surface of the upper horizontal member of the frame and the top of the stationary bar.

Preferably, the bars are so mounted as to be relatively readily removableto replace a damaged barand reassembleable within the screen panel.

The inventive concept representing both process and apparatus aspects of the improvement will become more apparent from the following detailed description of pre' ferred embodiments thereof and from the accompanying drawings wherein:

FIG. 1 is a view in central vertical section of the lower discharge end of a shaft type furnace in which the novel pellet cooling apparatus is installed;

FIG. 2 is also a view in vertical section of the lower part of the shaft type furnace taken on line 2-2 of FIG. 1;

FIG. 3 is a section on line 33 of FIG. 4 showing structural details of one of the air disengaging screens incorporated in the wall of the discharge end of the furnace; the view being drawn to an enlarged scale;

FIG. 4 is a horizontal view partly in section and partly in plan showing the screen of FIG. 3 together with the means for oscillating the movable bars thereof;

FIG. 5 is a vertical section of one of the screens and the wall portion of the furnace shaft associated therewith together with means for oscillating the movable bars of the screen;

FIG. 6 is a side elevation looking to the right in FIG. 5;

FIGS. 7 and 8 are side and end views, respectively, of one of the stationary bars incorporated in each screen;

FIGS. 9 and 10 are side and end views respectively of one of the movable, i.e. oscillatable, bars incorporated in the screen;

FIG. 11 is a fragmentary sectional view illustrating at an enlarged scale the details of construction and mountings for a few of the stationary and movable bars of the screen;

FIG. 12 is a fragmentary view showing a modified arrangement for oscillating the pivotally mounted movable bars utilizing a cam arrangement operating directly upon the individual movable bars in lieu of a reciprocating yoke coupled to the pivotally mounted movable bars in accordance with the embodiment illustrated in FIGS. 1-11; and

FIG. 13 is a vertical section showing the cam shaft of FIG. 12 and the manner in which it cooperates with the stationary and movable bars of the screen.

With reference now to the drawings and to FIGS. 1 and 2 in particular, the lower, convergently tapered portion of the vertical shaft furnace is indicated at 10. This tapered portion is seen to be rectangular in horizontal section and is constituted by four planar converging walls, 11, 12, 13 and l t. Extending between opposite walls 11, 13 is the means by which cooling gas is introduced into this part of the furnace. Such cooling gas introducing means can take various forms and the particular form illustrated is seen to be comprised of an inlet pipe 15 terminating at an opening 16 through wall 11 leading to the interior of the shaft. The wall opening 16 is seen to be oblong in configuration with its long sides arranged generally vertical and cooling air supplied through pipe 15 flows between two sets of louvers indicated at 17, 13 respectively which extend for the full distance between the opposite walls 11 and 13. As is seen in FIG. 2, the space between the two sets of louvers is closed at the bottom by means of a fiat plate 1% and is similarly closed at the top by means of a semicircular hood 20. Thus, all gas, preferably air entering the lower part of the shaft through inlet 16 will be caused to pass outwardly through the two sets of louvers along paths as generally indicated by the arrows in FIG. 2.

This air flows in a generally lateral direction through the column of descending pellets 21 in the shaft. These pellets are not shown but it is to be understood that the entire cross section of the shaft is substantially filled at all times with these pellets.

For disengaging the air or other cooling gas from the column of pellets, the invention provides a screen structure set into each of the two other opposite converging walls 12 and id. These screen structures designated generally at 22 and 23, are identical and hence a detailed description of one of them is believed to be sufficient. The two screen structures are located at about the same level in the shaft as the air inlet louver sets 17, 18 so that the air or other pellet cooling gas will flow in a generally lateral direction. In the present embodiment, the screen structures 22, 23 are located slightly above the louvers but this arrangement is preferred to better ensure removal of substantially all cooling air through the screens so that a minimum of the air is carried upwardly through the pellet column above the level of the screens.

The structural details of each screen are readily seen in FIGS. 3 and 4. With reference to these views each screen includes an outer rectangular frame 24 set into an opening 25 of like dimensions in the shaft wall. An inner rectangular frame 26 slightly smaller along all sides than frame 25 is set into the latter by means of a plurality of bolts 2'7.

As more particularly shown in FIG. 5, the confronting upper and lower faces 3t 31 of frame 26 are provided with ribs 32, 33 respectively, which serve to anchor a part of the components of the screen per se. The parts so anchored are a plurality of stationary bars 35, each of which stationary bars is separated from the serially next stationary bar by a movable (e.g., oscillatable or rotatable) bar 36.

Adjacent the slightly thickened upper end of each stationary bar 35 and extending laterally from either side of the same are stub bearing shafts 37, 37 each of which extends beyond the face of the bar not more than one half the thickness of the upper end of a movable bar 35. There is provided in side member 38 of inner frame 26 a recess 39 which accommodates a stub bearing shaft 37 of a stationary bar. In the slightly thickened upper end of each movable bar 36 there is formed a similar recess 40 which accommodates the confronting stub bearing shafts 3'], 37 of two adjacent stationary bars. Each stationary bar 315 is notched at top and bottom, as shown at 42 and 43, respectively, to receive ribs 32 and 33 with an easy fit. Bar 35 and its upper and lower notches 42, 43 are dimensioned to tolerate expansion in use whilst avoiding binding of parts.

Movable bars 36 are sufficiently shorter than are bars 35 to avoid contact with ribs 3t) and 31.

Stationary bars 35 are provided, intermediate their ends, with spacer buttons 54, 44 which enlarge the effective thickness of the bar to that of the aforesaid head portion. Similarly bars 36 are provided with rearwardly extending apertured lugs 45 yielding an effective thickness of the movable bar, at this point, equal to that of its head. Each screen is in two sections, each section including an array of alternate stationary and movable bars there being a stationary bar on each end of the array. The two arrays of bars are spaced apart by a center spacer bar 46 having a width a trifle greater than is the thickness of a stationary bar 35 plus its two stub bearing shafts 37.

The aforesaid array is assembled as follows: a first stationary bar 35 is slid over ribs 30 and 31 and to the left (or, right) until one of its stub bearing shafts 37 is inserted in recess 39 of the frame. Then, a first movable bar 36 is placed adjacent the so-positioned stationary bar, with its recess 40 fitted over the stub bearing shaft 37 on the rear side of bar 35. Then, asecond stationary bar is slid over said ribs and to the right until one of its stub bearing shafts 37 enters recess 40 in movable bar 36. This alternation of stationary and movable bars is repeated until the side is substantially closed, the final bar in this section being a stationary bar. Similarly the other half (e.g., in this example the right hand half) of the section is closed with an array of alternate stationary and movable bars there being one more stationary than movable bars in the array. There remains, between the two arrays a center space which is then filled by inserting center spacer bar 46, which latter is provided with recesses to accommodate the stub bearing shafts extending into said center space from the two end stationary bars of the two arrays. Finally, securing plates 47, 47, are bolted into place along inner frame 26 and over center spacer bar 46 to lock the bars of the two arrays in place.

The screening bars, both stationary and movable, preferably have a width of about 3 inches and are tapered from the inner end (i.e., the end adjacent the column of pellets) toward the outer end, in the interest of providing unimpeded passage through the slotindicated at 48- between any two adjacent bars, of any particle (e.g.,

fragment of a pellet) which migrates from the column through the inner mouth of said slot. This taper, which may best be viewed in FIG. 4, mayas shownbe symmetrical '(i.e., same on both sides): in the alternative, each bar may be beveled on one side wall only. In either event, the bar is about three-fourths inch thick at the inner edge (adjacent the pellets column) and about threeeighths inch thick at the remote edge.

All of the movable bars included in an array or section of a screen are tied together by means of a tie bar 51 which is passed through the apertures 52 of lugs 45 extending from movable bars 36. Tie bar 51 is coupled to a yoke member 55 by a plurality (four shown) of yoke arms 56 oscillatably secured to tie bar 51. ,Rearwardly from yoke member 55 there extends a yoke shaft 57 which is adapted to be reciprocated by means about to be described.

On the outside of furnace walls 12, 14 at least coextensive in height and width with the aforesaid screen structures 22, 23, there are provided air disengage chambers 60, 60, each having a top wall 61, side walls 62, 62, a bottom wall 63 and front wall 64. Front wall 64 preferably is secured (in gas tight manner) to top 61, sides 62, 62 and bottom wall 63 by means of gasketed joints with cooperating flanges secured together by bolts and nuts (not shown) in bolt holes 65, so as to provide ready access to the pair of screen sections constituting the screen structure within chamber 60. Discharge conduits, indicated at 68, communicate between the interiors of chambers 60, 6t) and any suitable reservoir or receptacle for dust-laden air. The bottom wall 63 merges into a depending dust leg 69 into the lower end of which latter there is provided a dump door or valve '70.

Mounted on the exterior face of front wall 64 of chamber 60 is a common drive mechanism for imparting re ciprocatory movement to the pair of yoke shafts 57, 57. This mechanism comprises a double-acting pneumatic cylinder 73, having at opposite ends thereof control inlet members diagrammatically represented at 74, 74 to rei ceive valved conduits (not shown) for pressure fluid to '73 from a source not shown, said cylinder having a piston and piston rod indicated at 75, the outer end of which (outer) ends of yoke shafts 57, 57, which latter extend through front wall 64 of chamber 60 by way of packed glands 93, 93.

In operation, cooling air is forced, through inlet pipe 15 into louvered air discharger 17, 18, 19, 20, and thence toward walls 12 and 14 and to screen structures 22 and 23, in which course the air becomes dust laden and highly heated by direct heat exchange from the highly heated pellets the interstices of which are traversed by V the cooling air current. The dirty, hot spent cooling air passes'through the slots 48, 48 between stationary bars 35 and movable bars 36 and thence into chamber 60, exiting through conduit 68.

As often as needfule.g., two complete cycles per each 4 hours, at a rate of 8-10 seconds per cyclethe control mechanism 74 actuates the motor (cylinder 73 and piston and piston rod '74) and thereby imparts reciprocatory movement to yoke shaft 57 and oscillates the movable rods of the screens through a stroke of restricted length (e.g., one-half inch). Particles thus dislodged from the mouths. of the slots drop into the dust leg 69 and eventually are drawn off through dump door 70.

It is an easy matter to replace a damaged bar from the screen, it being necessary merely to remove securing plates 47, withdrawn center spacer bar 46, and then one at a timeremove the alternate stationary and movable bars until the damaged bar is reached and removed and replaced by a perfect bar, whereupon the screen is reconstructed as described hereinbefore.

In lieu of the yoke arrangement described above, we can oscillate the movable bars of the screen by means of a cam mechanism, as illustrated in FIGS. 12and 13. In

this alternative embodiment, a cam shaft is used, the shaft being provided with lobes, alternately on the left hand side of the shaft and on the right hand side, one set of lobes, indicated at 100m, cooperating with the movable bars 36 and the other set of lobes indicated at 100s, these latter lobes being displaced from lobes 100m, cooperating with the stationary bars. The cam shaft is maintained in contact with the bars by means of C clamps 104 secured (e.g., Welded) to the stationary bars. Cam shaft 100 is rotated in bearings 105, by conventional rotational means (not shown), to impart oscillatory movement to the moveable bars at desired intervals. In so imparting movement, when lobe 100112 is in the position shown in FIG. 13 it has pressed movable bars 36 inwardly of the furnace, whereas when the cam shaft has been rotated 180 lobe 100s is brought adjacent stationary bar 35 thereby moving the cam shaft and,

. hence, the C clamp to the right thus returning'movable bar 36 to in-line position with respect to stationary bar 35.

What we claim is: 1 1. In a process of treating pellets of finely divided solid material involving feeding the pellets to the upper part of a column of such pellets gravitationally descending through a generally vertical shaft-type indurating furnace, heating the pellets in the upper part of said column through slotted screens in confronting Walls of the furnace parts of said slotted screens being oscillatable, and oscillating said oscillatable screen parts at intervals sufiiciently frequent to prevent stoppage of the slots of the screens by solid particles lodged in said slots.

2. A fluid-disengaging screen mechanism operable for use in a treating furnace having a Wall which, in use, is contacted by a body of fluent solid material through which body a fluid is passed, said fluid-disengaging screen mechanism being disposed in said furnace wall and comprising a plurality of an array of substantially parallel generally vertically disposed bars spaced apart to provide between adjacent bars slot-like open spaces having a width predetermined to provide screening and gas-disengaging functions, some of said bars being movable to a limited extent relative to adjacent stationary bars, and motion-effecting means operatively associated with the movable bars for periodically effecting relative motion between said movable bars and said adjacent stationary bars to dislodge any material tending to obstruct said open spaces.

3. The screen mechanism defined in claim 2, in which alternate bars are movable, in which said movable bars are pivoted at their upper ends for oscillation toward and away from the furnace interior, and in which said motion-effecting means is operatively associated with said movable bars at loci intermediate the ends of the movable bars.

4. The screen mechanism defined in claim 2, in which the motion-effecting means consists essentially of a reciprocating motor and linkage means connecting the same with said movable bars.

5. The screen mechanism defined in claim 4, in which the reciprocating motor is a hydraulic cylinder and associated piston.

6. The screen mechanism defined in claim 2, in which the motion-effecting means consists essentially of a cam device secured to the stationary bars and adapted to oscillate the movable bars.

7. The screen mechanism defined in claim 2, further characterized in that the array of bars is disposed in a generally vertical demountable frame having a top mem her, two side members and a bottom member, the confronting faces of said top and bottom members carrying generally horizontal upper and lower ribs substantially coextensive with said top and bottom members, and in that said stationary bars are notched at top and at bottom loosely fitting over said ribs whereby to fix said stationary bars in place.

8. The screen mechanism defined in claim 2, further characterized in that the array of bars is disposed in a generally vertical demountable frame having a top member, two side members and a bottom member, the confronting faces of said top and bottom members carrying generally horizontal upper and lower ribs substantially coextensive with said top and bottom members, in that said stationary bars are notched at top and at bottom loosely fitting over said ribs whereby to fix said stationary bars in place, and in that said movable bars are shorter than the stationary bars by the sum of the heights of said upper and lower ribs and are pivotally connected, adjacent their tops, to said stationary bars for limited oscillation about the pivot points.

9. The screen mechanism defined in claim 8, in which pivotal connection between stationary bars and movable bars is provided by stub bearing shafts outstandingfrom the sides of the stationary bars adjacent their tops and cooperating recesses in the movable bars.

10. The screen mechanism defined in claim 2 in which each of said stationary and movable bars is tapered from 10 that edge thereof which, in use, is adjacent the furnace space to that edge thereof which, in use, is remote from such furnace space.

11. In a generally vertical shaft-type treating furnace having walls which confront each other, said furnace including means in the upper part of the furnace for introducing heating gas thereinto and means in the lower part of the furnace for forcing a current of cooling gas therethrough, a cooling gas-introducing means Within the lower part of the furnace and intermediate confronting walls of the furnace, at least two gas-disengaging means let into confronting walls of the furnace generally opposite said cooling gas-introducing means, said gas-disengaging means comprising screens disposed in said confronting walls and composed of an array of substantially parallel generally vertically disposed bars spaced apart to provide between adjacent bars slot-like open spaces having a width predetermined to provide screening and gasdisengaging functions, some of said bars being movable to a limited extent relative to adjacent stationary bars, and motion-effecting means operatively associated with the movable bars for periodically effecting relative motion between said movable bars and said adjacent stationary bars to dislodge any material tending to obstruct said open spaces.

12. In a generally vertical shaft-type treating furnace having walls which confront each other, said furnace including means in the upper part of the furnace for introducing heating gas thereinto and means in the lower part of the furnace for forcing a current of cooling gas therethrough, a cooling gas-introducing means within the lower part of the furnace and intermediate confronting walls of the furnace, at least two gas-disengaging means let into con-fronting walls of the furnace generally opposite said cooling gas-introducing means, said gas-disengaging means comprising screens composed of substantially parallel generally vertically disposed bars spaced apart to provide between adjacent bars slot-like open spaces having a width predetermined to provide screening and gas-disengaging functions, some of said bars being movable to a limited extent and the others being stationary, and motion-effecting means operatively associated with the movable bars for periodically effecting relative motion between movable and stationary bars to dislodge any material tending to obstruct said open spaces.

13. The furnace defined in claim 12, in which alternate bars are movable, in which said movable bars are pivoted at their upper ends for oscillation toward and away from the furnace interior, and in which said motion-effecting means is operatively associated with said movable bars at loci intermediate the ends of the movable bars.

14. The furnace defined in claim 13, in which the motion-effecting means consists essentially of a reciprocating motor and linkage means connecting the same with said movable bars.

15. The furnace defined in claim 14, in which the reciprocating motor is a hydraulic cylinder and associated piston.

16. The furnace defined in claim 13, in which the motion effecting means consists essentially of a cam device secured to the stationary bars and adapted to oscillate the movable bars.

References Cited by the Examiner UNITED STATES PATENTS 2,676,095 4/ 54 De Vaney et al 263-29 2,744,743 5/56 Beggs et al 263-29 2,934,476 4/60 Zvej-nie'ks 34 --72 CHARLES SUKALO, Primary Examiner. 

1. IN A PROCESS OF TREATING PELLETS OF FINELY DIVIDED SOLID MATERIAL INVOLVING FEEDING THE PELLETS TO THE UPPER PART OF A COLUMN OF SUCH PELLETS GRAVITATIONALLY DESCENDING THROUGH A GENERALLY VERTICAL SHAFT-TYPE INDURATING FURNACE, HEATING THE PELLETS IN THE UPPER PART OF SAID COLUMN AND THEREAFTER COOLING THE PELLETS BY FORCING A CURRENT OF COOLING GAS THROUGH SUCH PELLETS COLUMN AND FINALLY DISCHARGING THE SO-COLLED PELLETS FROM THE FURNACE THE IMPROVEMENT WHICH CONSISTS IN INTRODUCING THE COOLING GAS INTO THE COLUMN INTERMEDIATE CONFRONTING SIDES OF THE COLUMN, LATERALLY DISENGAGING THE COOLING GAS FROM THE COLUMN THROUGH SLOTTED SCREENS IN CONFRONTING WALLS OF THE FURNACE PARTS OF SAID SLOTTED SCREENS BEING OSCILLATABLE AND OSCILLATING SAID OSCILLATABLE SCREEN PARTS AT INTERVALS SUFFICIENTLY FREQUENT TO PREVENT STOPPAGE OF THE SLOTS OF THE SCREENS BY SOLID PARTICLES LODGED IN SAID SLOTS. 